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Warming a question of degree

Temperatures have gone up over the last century in Grand Junction, but maybe not quite the way a recent climate map published in the New York Times would have one believe.

A Times article on the new National Climate Assessment released Tuesday by the White House included a map that compared average temperatures from 1901 to 1960 to average temperatures from 1991 through 2012. The Times map was based on a National Climatic Data Center map in the assessment that did not list data by cities. The Times map listed an increase of 3.2 degrees Fahrenheit in average temperature in Grand Junction in the 1991-2012 aggregate compared to the city’s 1901-1960 average.

It’s possible the map labeled Grand Junction as regional context, but used temperature data from the Western Slope and possibly eastern Utah, as the areas are all linked in a red spot on the map meant to signify an increase of at least 2 degrees from the first set of years to the next.

Aligning actual temperature data from local weather-watchers with the Times map is difficult to do.

The city’s average temperature measured by the National Weather Service at Grand Junction Regional Airport increased from 52.6 degrees in the 1901-1960 time period to 53.2 degrees for 1991-2012, according to Jeff Colton with the National Weather Service. Colton said minimum temperatures increased from 49.9 degrees in the 59-year cohort to 51.1 degrees in the 21-year cohort, while maximum temperatures went from 57.4 down to 55.2.

Broken down into seasons, the average January through March temperature in Grand Junction has increased from 34 in 1901-1960 to 36.1 in the same months of 1991-2012. April through June averages increased from 61.9 to 62.3 degrees, July through September averages went from 73.5 to 74.1 degrees, and the averages for October through December dipped slightly from 40.9 to 40.5 degrees.

Minimum temperatures increased by 5 degrees in the winters of 1991-2012 compared to the winters of 1901-1960. Temperatures went up by nine-tenths of a degree for spring, increased 1.8 degrees for summer, and went up by 2.4 degrees for autumn.

“You can definitely see an increase in minimum temperatures but the maximum temperature actually got cooler, except for summer,” Colton said.

The multi-page National Climate Assessment, posted in its entirety at http://www.globalchange.gov/ncadac, covers potential impacts of temperature and precipitation changes by region on water resources, agriculture, forests, human health, transportation, energy, biodiversity and ecosystems, urban and rural areas, and biochemical cycles. Climate change mitigation, research and adaptation are also discussed in the scientific study.